The discovery of nine new planets challenges the reigning theory of the formation of planets, according to new observations by astronomers, 2 of which for our own Dr Rachel Street and Dr Tim Lister .
Unlike the planets in our solar system, two of the newly discovered planets are orbiting in the opposite direction to the rotation of their host star. This upsets the primary theory of how planets are formed. The planets are called “exoplanets” because they are located outside of our solar system.
These and other related discoveries are being presented at the UK National Astronomy Meeting in Glasgow, Scotland, this week. This is the first public mention of the new planets and the research will be described in upcoming scientific journal articles.
“Planet evolution theorists now have to explain how so many planets came to be orbiting like this,” said Tim Lister, a project scientist at LCOGT. Lister leads a major part of the observational campaigns along with Rachel Street of LCOGT, Andrew Cameron of the University of St. Andrews in Scotland, and Didier Queloz, of the Geneva Observatory in Switzerland.
Data from LCOGT was instrumental in confirming the new planet discoveries. By adding these nine new “transiting” planets, the number of known transiting planets has grown from 71 to 80. A transit occurs when a celestial body passes in front of its host star and blocks some of the star's light. This type of eclipse causes a small drop in the apparent brightness of the star and enables the planet's mass, diameter, density, and temperature to be deduced.
After the initial detection of the new exoplanets by the Wide Angle Search for Planets (WASP), the team of astronomers combined data from LCOGT’s 2.0-meter Faulkes Telescopes in Hawaii and Australia with follow-up from other telescopes to confirm the discoveries and characterize the planets.
The planets are revolving around nearby stars within 1,000 light years of our galaxy. Their stars are located in the constellations Pegasus, Virgo, Pisces, and Andromeda, in the northern hemisphere, and Eridanus, Hydra, Cetus, and Phoenix, in the southern hemisphere.
The nine planets are called “Hot Jupiters.” The planets are orbiting other stars that have masses similar to that of Jupiter, but they orbit their parent stars much more closely than any of the planets in our solar system. In the 15 years since the first Hot Jupiters were discovered, their origin has been a puzzle. Because they are both large and close, they are easier to detect from their gravitational effect on their stars and more likely to transit the disk of the star. Most of the first exoplanets that were discovered were of this type.
The cores of giant planets are thought to form from a mix of rock and ice particles found only in the cold outer reaches of planetary systems. Hot Jupiters, therefore, must form far from their star and subsequently migrate inwards over the course of a few million years. Many astronomers believed this could happen due to gravitational interactions with the disk of dust from which they formed, and which might also subsequently form Earth-like rocky planets. However, these new results suggest this may not be the whole story because it does not explain how planets end up orbiting contrary to the orbit of the disk.
The best alternative migration theory suggests that the proximity of Hot Jupiters to their stars is not due to interactions with the dust disk at all, but to a slower evolution involving a gravitational tug-of-war with more distant planetary or stellar companions over hundreds of millions of years, according to the research team. Bounced onto a tilted and elongated orbit, a wandering gas giant would suffer tidal friction every time it swung close to the star, eventually becoming parked in a near circular, but randomly tilted orbit close to the star. “In this scenario, smaller planets in orbits similar to Earth's are unlikely to survive,” said Rachel Street.
LCOGT's flexible approach to scheduling means the network provides responsive and highly efficient follow-up for large-scale surveys such as WASP. LCOGT is affiliated with neighboring UC Santa Barbara.
